Short Circuiting Structure For Lithium Secondary Battery Having Excellent Stability Against Overcharge And Pouch Type Lithium Secondary Battery Comprising The Same

ABSTRACT

Disclosed herein are a short circuit structure for mechanically cutting an electrode tab and/or an electrode lead of a pouch-shaped battery cell in order to secure the safety of the pouch-shaped battery cell when the pouch-shaped battery cell swells due to gas generated in the pouch-shaped battery cell while the pouch-shaped battery cell is in an abnormal state or when the pouch-shaped battery cell is overcharged, and a pouch-shaped secondary battery including the same. Current is prevented from flowing in the pouch-shaped secondary battery when the pouch-shaped secondary battery is overcharged or when the pouch-shaped secondary battery is in an abnormal state. In addition, a reduction in the energy density of the pouch-shaped secondary battery is prevented when a voluminous device is further provided in the pouch-shaped secondary battery.

TECHNICAL FIELD

The present invention relates to a short circuit structure for securingthe safety of a battery and a pouch-shaped secondary battery includingthe same, more particularly to a short circuit structure formechanically cutting an electrode tab and/or an electrode lead of apouch-shaped battery cell to secure the safety of the pouch-shapedbattery cell when the pouch-shaped battery cell swells due to gasgenerated in the pouch-shaped battery cell while the pouch-shapedbattery cell is in an abnormal state or when the pouch-shaped batterycell is overcharged, and to a pouch-shaped secondary battery includingthe same.

BACKGROUND ART

In general, there are various kinds of secondary batteries, such as anickel cadmium battery, a nickel hydride battery, a lithium ion battery,and a lithium ion polymer battery. Such secondary batteries have beenused in large-sized products that require high output, such as anelectric vehicle and a hybrid electric vehicle, a power storage devicefor storing surplus power or new and renewable energy, and a backuppower storage device. Secondary batteries also used in small-sizedproducts, such as a digital camera, a portable digital versatile disc(DVD) player, an MP3 player, a personal digital assistant (PDP), aportable game device, a power tool, and an electric bicycle (E-bike).

A lithium secondary battery is charged and discharged through a processin which lithium ions from a lithium metal oxide of a positive electrodeare repeatedly intercalated into a negative electrode, such as agraphite electrode, and the lithium ions are repeatedly deintercalatedfrom the negative electrode.

Heat may be generated from such a lithium secondary battery due to ashort circuit by external impacts, the overcharge or the overdischargeof the lithium secondary battery. As a result, an electrolyte may bedecomposed into gas in the lithium secondary battery, and thermalrunaway could occur in the lithium secondary battery. These are severalaspects for safety of the lithium secondary battery. In particular, thesecondary battery may explode for various reasons. In one example, thesecondary battery may explode due to an increase in the pressure of airin the secondary battery, which is caused by the decomposition of anelectrolyte. Specifically, when the secondary battery is repeatedlycharged and discharged, gas may be generated in the secondary battery asthe result of the electrochemical reaction between the electrolyte andan electrode active material. The gas generated in the secondary batteryincreases the pressure in the secondary battery. As a result, thefastening force between parts constituting the secondary battery may bereduced, the external case of the secondary battery may be damaged, aprotection circuit of the secondary battery may be operated early, anelectrode of the secondary battery may be deformed, a short circuit mayoccur in the secondary battery, or the secondary battery may explode.

In order to secure the safety of such a battery when the battery isovercharged, overcurrent is prevented from flowing in the batterythrough the control of electronic parts, whereby the battery isprevented from being overcharged. To this end, a protection circuit,such as a protection circuit module (PCM), may be applied to thebattery. Even in the case in which such an overcharge protectioncircuit, such as a PCM, is applied to the battery, however, it isdifficult to sufficiently secure the safety of the battery. Inparticular, it is necessary for a pouch-shaped battery to be providedwith a further improved protection circuit structure in order to moreaccurately check the swelling of the pouch-shaped battery.

In addition, there has been used a mechanical current interrupt devicethat physically interrupts the series connection of a battery pack usingthe pressure generated in the battery due to thermal expansion of thebattery when the battery is overcharged in consideration of malfunctionof the electronic parts of the battery. Generally, in the currentinterrupt device of the battery pack, there is widely used a method ofphysically cutting the series connection of the battery pack through thestructure of the battery pack using only the pressure generated in thebattery as the battery is expanded when the battery is overcharged inorder to interrupt the flow of current in the battery pack. However, ashort circuit formation unit that is capable of interrupting the flow ofcurrent in a pouch-shaped battery when the volume of the pouch-shapedbattery is increased has not been suggested.

Korean Patent Application Publication No. 2016-0129763 (Nov. 9, 2016)discloses a lithium secondary battery including a positive electrodeplate, a separator, and a negative electrode plate, which aresequentially stacked, an electrode tab extending from one side of eachof the positive electrode plate and the negative electrode plate by apredetermined length, and an electrode lead electrically connected tothe electrode tab, wherein a welded portion is provided at at least aportion of a region between the electrode tab and the electrode leadunder a normal operating condition of the lithium secondary battery andwherein the welded portion is cut under an abnormal operating conditionof the lithium secondary battery, for example when the temperature ofthe lithium secondary battery is high. However, any unit correspondingto a short circuit formation unit for separating two-level concave andconvex electrode leads, connected to each other via a conductiveadhesive, from each other when the volume of a pouch-shaped battery caseis increased is not suggested.

Korean Registered Patent No. 10-1601123 (Mar. 8, 2016) discloses asecondary battery including an electrode assembly and a battery case, inwhich the electrode assembly is provided in a sealed state such that theelectrode assembly is isolated from the outside, wherein the secondarybattery further includes a first electrode lead, having one endconnected to the electrode assembly so as to protrude from the electrodeassembly and the other end exposed outward from the battery case, and asecond electrode lead, detachably connected to the first electrode lead,the second electrode lead extending from the inside of the battery caseto the outside of the battery case so as to be exposed outward from thebattery case, and wherein an adhesive portion for coupling the firstelectrode lead and the second electrode lead is provided outside thebattery case. However, any unit corresponding to a short circuitformation unit for cutting an electrode tab and an electrode lead whenthe volume of a pouch-shaped battery case is increased is not suggested.Korean Registered Patent No. 10-1614434 (May 2, 2016) discloses abattery cell having an overcurrent interrupt function, the battery cellincluding an electrode assembly, an electrode lead connected to theelectrode assembly, the electrode lead including a first metal plate anda second metal plate located so as to be spaced apart from each other bya predetermined gap and an alloy bridge for filling the gap between thefirst metal plate and the second metal plate, the alloy bridge having amelting point lower than the melting points of the first metal plate andthe second metal plate, a cell case for receiving the electrode assemblysuch that the electrode lead is exposed outward, and a CTR terminalconnected between opposite ends of the battery cell for causing a shortcircuit outside the battery cell when the temperature of the batterycell exceeds a predetermined temperature, wherein the alloy bridgeexhibits electrical resistance higher than the electrical resistances ofthe first metal plate and the second metal plate, and wherein the alloybridge is located outside the cell case. However, any unit correspondingto a short circuit formation unit for separating two-level electrodeleads, connected to each other via a conductive adhesive, from eachother when the volume of a pouch-shaped battery case is increased is notsuggested.

Korean Patent Application Publication No. 2012-0139590 (Dec. 27, 2012)discloses a part for secondary batteries including a lead-free solderingbridge having a melting point of 150 to 300° C., the lead-free solderingbridge being mainly made of tin (Sn) and copper (Cu), and a first metalplate and a second metal plate joined to the lead-free soldering bridgein the state of being spaced apart from each other by a small gap.However, any unit corresponding to a short circuit formation unit forseparating two-level electrode leads, connected to each other via aconductive adhesive, from each other when the volume of a pouch-shapedbattery case is increased is not suggested.

Japanese Patent Application Publication No. 2011-249128 (Dec. 8, 2011)discloses a temperature fuse including a pair of lead conductorsopposite each other in the state of being spaced apart from each otherin a longitudinal direction, a pair of notches formed in opposite endsof the lead conductors so as to face outward in the longitudinaldirection, and a joint for joining the lead conductors by welding theopposite ends of the lead conductors using a low melting-point solublealloy, wherein the size of each of the notches in the longitudinaldirection is set to be equal to or greater than the size of the joint inthe longitudinal direction. However, any unit corresponding to a shortcircuit formation unit for separating two-level concave and convexelectrode leads, connected to each other via a conductive adhesive, fromeach other when the volume of a pouch-shaped battery case is increasedis not suggested.

Korean Patent Application Publication No. 2015-0074439 (Jul. 2, 2015)discloses a battery overcharge safety device including a battery stackconstituted by a plurality of cells, a safety circuit electricallyconnected to two or more cells of the battery stack, the safety circuithaving an interrupting means for selectively interrupting the electricalconnection of the cells, and a closed circuit provided between the cellsconnected to the safety circuit, the closed circuit having a switchingmeans for selectively switching the electrical connection of the cellswhen the cells swell, wherein the switching means is pushed and turnedON to open the interrupting means of the safety circuit and theelectrical conduction between the cells is achieved through theswitching means when the cells swell, and wherein the switching means isturned OFF and the electrical conduction between the cells isinterrupted when the cells swell further. However, any unitcorresponding to a short circuit formation unit for separating two-levelconcave and convex electrode leads, connected to each other via aconductive adhesive, from each other when the volume of a pouch-shapedbattery case is increased is not suggested.

That is, a short circuit formation unit for short-circuiting apouch-shaped secondary battery when the pressure in the batteryincreases or when the volume of the battery increases in an abnormalstate of the battery, for example in the case in which the battery isovercharged or in the case in which gas is generated in the battery, inorder to secure the safety of a pouch-shaped battery and a pouch-shapedsecondary battery including the same have not been suggested.

RELATED ART DOCUMENT Patent Document 0001

Korean Patent Application Publication No. 2016-0129763 (Nov. 9, 2016)

Patent Document 0002

Korean Registered Patent No. 10-1601123 (Mar. 8, 2016)

Patent Document 0003

Korean Registered Patent No. 10-1614434 (May 2, 2016)

Patent Document 0004

Korean Patent Application Publication No. 2012-0139590 (Dec. 27, 2012)

Patent Document 0005

Japanese Patent Application Publication No. 2011-249128 (Dec. 8, 2011)

Patent Document 0006

Korean Patent Application Publication No. 2015-0074439 (Jul. 2, 2015)

DISCLOSURE Technical Problem

The present invention has been made in view of the above problems, andit is an object of the present invention to provide a short circuitstructure for mechanically cutting an electrode tab and/or an electrodelead of a pouch-shaped battery cell in order to secure the safety of thepouch-shaped battery cell when the pouch-shaped battery cell swells dueto gas generated in the pouch-shaped battery cell while the pouch-shapedbattery cell is in an abnormal state or when the pouch-shaped batterycell is overcharged, and a pouch-shaped secondary battery including thesame.

It is another object of the present invention to provide a simple shortcircuit structure that can be used instead of an additional device forinterrupting the flow of current in a battery cell in an abnormal stateof the battery cell, thereby maintaining the energy density of thebattery cell, and a pouch-shaped secondary battery including the same.

Technical Solution

In accordance with one aspect of the present invention, the above andother objects can be accomplished by the provision of a pouch-shapedsecondary battery configured to have a structure in which a unit cell,including a positive electrode plate, a separator, a negative electrodeplate, an electrode tab, and an electrode lead, or a cell assembly,constituted by two or more stacked unit cells, is received in apouch-shaped battery case, wherein the pouch-shaped secondary batteryincludes a short circuit structure constituted by two or more units,opposite ends of which are coupled to the electrode tab and/or theelectrode lead, for cutting the electrode tab and/or the electrode leadwhen the pouch-shaped battery case is deformed due to an increase in thevolume of the pouch-shaped battery case.

In addition, the short circuit structure may be configured such that thetwo or more units of the short circuit structure are separated from eachother to cut the electrode tab and/or the electrode lead when thepouch-shaped battery case is deformed due to an increase in the volumeof the pouch-shaped battery case.

In addition, the short circuit structure may be provided at apredetermined position thereof with a hole, through which the electrodetab and/or the electrode lead is inserted.

In addition, the short circuit structure may be formed at at least oneselected from among the electrode tab, the electrode lead, and theconnection between the electrode tab and the electrode lead.

In addition, the electrode tab may be a positive electrode tab, anegative electrode tab, or both the positive electrode tab and thenegative electrode tab.

In addition, the electrode lead may be a positive electrode lead, anegative electrode lead, or both the positive electrode lead and thenegative electrode lead.

In addition, the short circuit structure may include a concave unit anda convex unit, the concave unit and the convex unit being coupled toeach other.

In addition, at least one side surface of the short circuit structure,in which the hole is not formed, may be disposed so as to be in contactwith the pouch-shaped battery case.

In addition, the short circuit structure may be provided at at least onesurface of the hole formed therein, which contacts the electrode taband/or the electrode lead inserted into the hole, with a cutting layerfor cutting the electrode tab and/or the electrode lead.

In addition, the cutting layer may be made of at least one selected fromamong a metal material, a ceramic material, and a polymer resin.

In addition, the cutting layer, which contacts the electrode tab and theelectrode lead, may be formed so as to have at least one selected fromamong a quadrangular section, a circular section, a semicircularsection, a diamond-shaped section, an oblique section, a wave section, azigzag section, a sawtooth section, and an arbitrarily shaped section.

In addition, an increase in the volume (V_(short)) of the pouch-shapedbattery case for cutting the electrode tab and/or the electrode lead maysatisfy the condition of V_(short)>L on the assumption that a length ofone side surface of the short circuit structure is L.

In addition, an increase in the volume (V_(short)) of the pouch-shapedbattery case for cutting the electrode tab and/or the electrode lead maysatisfy the condition of Lc<0 on the assumption that a distance betweena positive electrode cutting layer and a negative electrode cuttinglayer of the short circuit structure is Lc.

In accordance with another aspect of the present invention, there isprovided a device including the pouch-shaped secondary battery describedabove. In addition, the device may be selected from the group consistingof an electronic device, an electric vehicle, a hybrid electric vehicle,and a power storage device.

Advantageous Effects

As is apparent from the above description, a short circuit structure forsecuring the safety of a battery when the battery is overcharged and apouch-shaped secondary battery including the same according to thepresent invention have the effect of preventing current from flowing inthe pouch-shaped secondary battery when the pouch-shaped secondarybattery is overcharged or in the state in which the pouch-shapedsecondary battery is in an abnormal state.

In addition, the present invention has the effect of preventing areduction in the energy density of the pouch-shaped secondary batterywhen a voluminous device is further provided in the pouch-shapedsecondary battery.

In addition, the present invention has the effect of cutting anelectrode tab and/or an electrode lead when the volume of thepouch-shaped secondary battery increases due to gas generated in thepouch-shaped secondary battery.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a view showing an illustrative conventional pouch-shapedbattery cell;

FIG. 2 is a view showing an increase in the volume of the illustrativeconventional pouch-shaped battery cell due to gas generated in thebattery cell;

FIG. 3 is a view showing a pouch-shaped secondary battery having a shortcircuit structure according to an embodiment of the present invention;

FIG. 4 is a sectional view showing the process in which a positiveelectrode tab is cut by the short circuit structure according to theembodiment of the present invention;

FIG. 5 is a perspective view showing the process in which the positiveelectrode tab is cut by the short circuit structure according to theembodiment of the present invention;

FIG. 6 is a sectional coupling view showing the short circuit structureaccording to the embodiment of the present invention;

FIG. 7 is a side coupling view showing the short circuit structureaccording to the embodiment of the present invention; and

FIG. 8 is a view showing a positive electrode short circuit structureaccording to an embodiment of the present invention, wherein thepositive electrode short circuit structure includes three units.

DETAILED DESCRIPTION OF THE INVENTION

Now, preferred embodiments of the present invention will be described indetail with reference to the accompanying drawings such that thepreferred embodiments of the present invention can be easily implementedby a person having ordinary skill in the art to which the presentinvention pertains. In describing the principle of operation of thepreferred embodiments of the present invention in detail, however, adetailed description of known functions and configurations incorporatedherein will be omitted when the same may obscure the subject matter ofthe present invention.

Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts. Meanwhile, in the casein which one part is ‘connected’ to another part in the followingdescription of the present invention, not only may the one part be‘directly connected’ to the another part, but also, the one part may be‘indirectly connected’ to the another part via a further part. Inaddition, that a certain element is ‘included’ means that other elementsare not excluded, but may be further included unless mentionedotherwise.

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 1 is a view showing an illustrative conventional pouch-shapedbattery cell.

In generally, a lithium secondary battery is manufactured as follows.First, a mixture of an active material, a binder, and a plasticizer isapplied to a positive electrode current collector and a negativeelectrode current collector in order to manufacture a positive electrodeplate and a negative electrode plate, respectively. Subsequently, aplurality of positive electrode plates and a plurality of negativeelectrode plates are stacked in the state in which separators areinterposed respectively between the positive electrode plates and thenegative electrode plates in order to manufacture a battery cell havinga predetermined shape. Subsequently, the battery cell is placed in abattery case, an electrolytic solution is injected into the batterycase, and the battery case is sealed, whereby a secondary battery, suchas a battery pack, is manufactured.

Electrode leads are connected to a general electrode assembly. Each ofthe electrode leads is configured to have a structure in which one endof the electrode lead is connected to the electrode assembly, the otherend of the electrode lead is exposed outward from the battery case, andthe battery case, in which the electrode assembly is placed, is sealedby an adhesive layer, such as a sealant layer, at the portion of thebattery case from which the electrode lead extends outward from thebattery case.

In addition, the electrode assembly is provided with electrode tabs.Each current collector plate of the electrode assembly includes a coatedpart, on which an electrode active material is coated, and a non-coatedpart, on which the electrode active material is not coated. Each of theelectrode tabs may be formed by cutting the non-coated part, or may be aseparate conductive member connected to the non-coated part byultrasonic welding. As shown, the electrode tabs may protrude in onedirection such that the electrode tabs are formed at the electrodeassembly so as to be arranged side by side. Alternatively, the electrodetabs may protrude in opposite directions.

Each electrode tab serves as a path along which electrons move betweenthe inside and the outside of the battery. Each of the electrode leadsis connected to a corresponding one of the electrode tabs by spotwelding. The electrode leads may extend in the same direction or inopposite direction depending on the position at which positive electrodetabs and negative electrode tabs are formed. A positive electrode leadand a negative electrode lead may be made of different materials. Forexample, the positive electrode lead may be made of the same material asthe positive electrode plate, such as an aluminum (Al) material, and thenegative electrode lead may be made of the same material as the negativeelectrode plate, such as a copper (Cu) material or a copper materialcoated with nickel (Ni). Finally, the electrode leads are electricallyconnected to external terminals via terminal parts thereof.

A pouch-shaped sheathing member contains the electrode assembly in asealed state such that a portion of each of the electrode leads, i.e.the terminal part of each of the electrode leads, is exposed from thepouch-shaped sheathing member. As previously described, the adhesivelayer, such as a sealant layer, is interposed between each of theelectrode leads and the pouch-shaped sheathing member. The pouch-shapedsheathing member is provided at the edge thereof with a sealed region. Ahorizontal slit of each of the electrode leads is spaced apart from thesealed region toward a joint. That is, in the case in which each of theelectrode leads is formed so as to have an inverted T shape, the legpart of the T shape protrudes outward from the pouch-shaped sheathingmember whereas a portion of the head part of the T shape is located inthe sealed region.

In general, a positive electrode current collector plate is made of analuminum material, and a negative electrode current collector plate ismade of a copper material. When a swelling phenomenon occurs, copperfoil tends to rupture more easily than aluminum foil. For this reason,the negative electrode lead may rupture more easily than the positiveelectrode lead. Preferably, therefore, the negative electrode lead isused as an electrode lead that is capable of rupturing.

In the normal state of the secondary battery, the electrode assembly isisolated from the outside due to the adhesive layer. When the pressurein the battery increases as the result of the overcharge of the batteryor an increase in the temperature of the battery, however, the batterycase may swell. At this time, the weak portion of the battery case orthe adhesion portion between another component of the secondary batteryand the battery case ruptures, whereby gas is discharged from thebattery.

As long as the electrode leads are electrically connected to theelectrode assembly, however, current continuously flows in the battery,making it very difficult to secure the safety of the battery. In orderto solve this problem, the amount of electrolyte that is injected intothe secondary battery may be adjusted, or the short circuit pressure ofa current interrupt device (CID) may be adjusted. In this case, however,the safety of the battery is reduced when the battery is overcharged.That is, it is difficult not only to secure the safety of the batterywhen the battery is overcharged but also to secure the battery when thebattery is used in a high-temperature situation.

Comparative Example

FIG. 2 is a view showing an increase in the volume of the illustrativeconventional pouch-shaped battery cell due to gas generated in thebattery cell.

A pouch-shaped battery case includes a gas barrier layer and a sealantlayer. The pouch-shaped battery case may further include a surfaceprotective layer, which is the outermost layer formed on the gas barrierlayer. The gas barrier layer is configured to prevent the introductionof gas into the battery cell. The gas barrier layer is mainly made ofaluminum (Al) foil. The sealant layer is the innermost layer of thepouch-shaped battery case, which contacts the member placed in thepouch-shaped battery case, i.e. the battery cell. The surface protectivelayer is mainly made of nylon resin in consideration of wear resistanceand heat resistance. The pouch-shaped battery case is manufactured byprocessing a film having the above stack structure into the shape of apouch. Components constituting the battery cell, such as positiveelectrodes, negative electrodes, and separators, are placed in thepouch-shaped battery case in the state of being impregnated with anelectrolytic solution. After the components constituting the batterycell are placed in the pouch-shaped battery case, the sealant layers aresealed by thermal bonding at the entrance of the pouch-shaped batterycase. Since each of the sealant layers contacts the componentsconstituting the battery cell, it is necessary for each of the sealantlayers to exhibit high insulation and high resistance to theelectrolytic solution. In addition, is necessary for each of the sealantlayers to exhibit high sealability to such an extent that thepouch-shaped battery case can be isolated from the outside. That is, itis necessary for the sealing portion of the pouch-shaped battery case atwhich the sealant layers are sealed by thermal bonding to exhibit highthermal adhesive strength. In general, a sealant layer is made of apolyolefin-based resin, such as polypropylene (PP) or polyethylene (PE).In particular, each of the sealant layers of the pouch-shaped batterycase is mainly made of polypropylene (PP), since polypropylene exhibitsexcellent mechanical properties, such as high tensile strength, highrigidity, high surface hardness, and high impact resistance, and highresistance to an electrolytic solution.

However, the conventional pouch-shaped secondary battery is unsafe fromthe aspect of explosion danger. In general, heat and pressure aregenerated in a battery cell while electricity is produced/used (i.e.charged/discharged) in the battery cell (i.e. while anoxidation-reduction reaction occurs in the battery cell). At this time,high heat and pressure may be generated in the battery cell due to theovercharge of the battery cell or the short circuit in the battery cell,which may be caused by an abnormal reaction in the battery cell. Thebattery cell may explode due to such high heat and pressure. Theconventional pouch-shaped secondary battery is not provided with anymechanical means that is capable of preventing the explosion of thesecondary battery. As a result, the conventional pouch-shaped secondarybattery is exposed to explosion danger.

Embodiment

FIG. 3 is a view showing a pouch-shaped secondary battery having a shortcircuit structure according to an embodiment of the present invention.

The present invention provides a pouch-shaped secondary batteryconfigured to have a structure in which a unit cell, including apositive electrode plate, a separator, a negative electrode plate, anelectrode tab, and an electrode lead, or a cell assembly, constituted bytwo or more stacked unit cells, is received in a pouch-shaped batterycase, wherein the pouch-shaped secondary battery includes a shortcircuit structure constituted by two or more units, opposite ends ofwhich are coupled to the electrode tab and/or the electrode lead, forcutting the electrode tab and/or the electrode lead when thepouch-shaped battery case is deformed due to an increase in the volumeof the pouch-shaped battery case.

The unit cell is a single cell.

The pouch-shaped secondary battery may further include an insulationtape. The insulation tape is attached to a predetermined portion of thepouch-shaped battery case at which the electrode tab contacts thepouch-shaped battery case in order to seal the pouch-shaped battery casewhile insulating the electrode tab from the pouch-shaped battery case.When the pouch-shaped battery case is sealed, the pressure at theportion of the pouch-shaped battery case at which the electrode tabcontacts the pouch-shaped battery case is relatively high. As a result,a casted polypropylene (CPP) layer of the pouch-shaped battery case maybe easily damaged. Consequently, an inner layer of the insulation tapeexhibits high mechanical strength and high heat resistance such that theshape of the insulation tape can be maintained, and thus electricalinsulation between pouch-shaped battery case and the electrode tab canbe maintained when the pouch-shaped battery case is sealed by fusion inthe state in which heat and pressure are applied to the pouch-shapedbattery case. In particular, the inner layer of the insulation tapeprevents aluminum foil of the pouch-shaped battery case fromelectrically contacting the electrode tab even when a portion of thealuminum foil of the pouch-shaped battery case is exposed during thesealing of the pouch-shaped battery case, whereby it is possible tomaintain the insulated state of the pouch-shaped battery case. An outerlayer of the insulation tape provides high adhesive force between thepouch-shaped battery case and the electrode tab even when a portion ofthe insulation tape is deformed in the state in which heat and pressureare applied to the pouch-shaped battery case, whereby it is possible tomaintain the sealed state of the pouch-shaped battery case. Therefore,even when the casted polypropylene (CPP) layer of the pouch-shapedbattery case is deformed due to heat and pressure during the sealing ofthe pouch-shaped battery case, whereby a portion of the aluminum foil ofthe pouch-shaped battery case is exposed, it is possible to maintain theinsulated state of the pouch-shaped battery case.

Consequently, it is not necessary for the pouch-shaped secondarybattery, which is provided with the short circuit structure, to have acurrent interrupt device (CID), which is required from a can-shapedsecondary battery.

In addition, the short circuit structure may be configured such that thetwo or more units of the short circuit structure are separated from eachother to cut the electrode tab and/or the electrode lead when thepouch-shaped battery case is deformed due to an increase in the volumeof the pouch-shaped battery case.

It is obvious that the coupling form of the units of the short circuitstructure and the number of units constituting the short circuitstructure are not particularly restricted, as long as the short circuitstructure is capable of cutting the electrode tab and/or the electrodelead.

In addition, the short circuit structure may be provided at apredetermined position thereof with a hole, through which the electrodetab and/or the electrode lead is inserted. The form of the hole of theshort circuit structure is not particularly restricted as long as theelectrode tab and/or the electrode lead can be inserted into the holeformed in the short circuit structure. For example, the hole may beformed so as to have a rectangular shape, a square shape, or a polygonalshape. When the electrode tab and/or the electrode lead is inserted intothe hole, the electrode tab and/or the electrode lead may come intocontact with at least one surface of the hole.

The material of the short circuit structure is not particularlyrestricted, as long as the short circuit structure is capable of cuttingthe electrode tab and/or the electrode lead. For example, the shortcircuit structure may be made of at least one selected from among apolymer resin, an inorganic material, and a metal material.

In addition, the short circuit structure may be formed at at least oneselected from among the electrode tab, the electrode lead, and theconnection between the electrode tab and the electrode lead.

In order to prevent current from flowing in the pouch-shaped secondarybattery by short circuiting the battery when the battery is overchargedor when the battery is in an abnormal state, the short circuit structuremay be formed at at least one selected from among the electrode tab, theelectrode lead, and the connection between the electrode tab and theelectrode lead. Preferably, the short circuit structure is formed at theelectrode tab. The short circuit structure physically cut at least oneselected from among the electrode tab, the electrode lead, and theconnection between the electrode tab and the electrode lead when thepouch-shaped battery case is abnormally expanded. Consequently, aplurality of short circuit structures may be provided in order toachieve the above purpose.

FIG. 4 is a sectional view showing the process in which a positiveelectrode tab is cut by the short circuit structure according to theembodiment of the present invention.

FIG. 5 is a perspective view showing the process in which the positiveelectrode tab is cut by the short circuit structure according to theembodiment of the present invention.

In addition, the electrode tab may be a positive electrode tab, anegative electrode tab, or both the positive electrode tab and thenegative electrode tab.

In addition, the electrode lead may be a positive electrode lead, anegative electrode lead, or both the positive electrode lead and thenegative electrode lead.

In addition, the short circuit structure may include a concave unit anda convex unit, which are coupled to each other.

The units constituting the short circuit structure may be coupled toeach other in various forms as long as the short circuit structure iscapable of physically cutting at least one selected from among theelectrode tab, the electrode lead, and the connection between theelectrode tab and the electrode lead when the volume of the pouch-shapedsecondary battery is increased in the abnormal state of the pouch-shapedsecondary battery. For example, each of the two or more units of theshort circuit structure may be provided with a hole, through which atleast one selected from among the electrode tab, the electrode lead, andthe connection between the electrode tab and the electrode lead isinserted. The holes formed in the two or more units of the short circuitstructure may have the same shape. When the volume of the pouch-shapedsecondary battery is increased, the units constituting the short circuitstructure may be separated from each other to physically cut at leastone selected from among the electrode tab, the electrode lead, and theconnection between the electrode tab and the electrode lead, whereby itis possible to prevent current from flowing in the pouch-shapedsecondary battery.

In addition, at least one side surface of the-short circuit structure,in which the hole is not formed, may be disposed so as to be in contactwith the pouch-shaped battery case.

If the side surface of the short circuit structure is not disposed so asto be in contact with a corresponding surface of the pouch-shapedsecondary battery in the normal state of the pouch-shaped secondarybattery, the two or more units of the short circuit structure may not beproperly separated from each other when the volume of the pouch-shapedsecondary battery is increased in the abnormal state of the pouch-shapedsecondary battery.

FIG. 6 is a sectional coupling view showing the short circuit structureaccording to the embodiment of the present invention.

FIG. 7 is a side coupling view showing the short circuit structureaccording to the embodiment of the present invention.

In addition, the short circuit structure may be provided at the at leastone surface of the hole formed therein, which contacts the electrode taband/or the electrode lead inserted into the hole, with a cutting layerfor cutting the electrode tab and/or the electrode lead.

In addition, the cutting layer may be made of at least one selected fromamong a metal material, a ceramic material, and a polymer resin. It isobvious that the material of the cutting layer exhibits sufficienthardness to physically cut at least one selected from among theelectrode tab, the electrode lead, and the connection between theelectrode tab and the electrode lead. In addition, it is obvious thatthe material of the cutting layer exhibits the above-mentioned hardnessand cutting force under a temperature and pressure of the pouch-shapedsecondary battery typical for the abnormal state of the pouch-shapedsecondary battery.

In addition, the cutting layer, which contacts the electrode tab and theelectrode lead, may be formed so as to have at least one selected fromamong a quadrangular section, a circular section, a semicircularsection, a diamond-shaped section, an oblique section, a wave section, azigzag section, a sawtooth section, and an arbitrarily shaped section.The cutting layer may have any of various shapes, as long as the cuttinglayer is capable of physically cutting at least one selected from amongthe electrode tab, the electrode lead, and the connection between theelectrode tab and the electrode lead.

In addition, the outermost thickness of the cutting layer may be smallerthan the thickness of the surface of the cutting layer that contacts theshort circuit structure. In addition, the outermost section of thecutting layer may be triangular. However, the shape of the outermostsection of the cutting layer is not particularly restricted, as long asthe cutting layer is capable of physically cutting at least one selectedfrom among the electrode tab, the electrode lead, and the connectionbetween the electrode tab and the electrode lead.

In addition, the present invention may provide an electronic deviceincluding a pouch-shaped secondary battery having the short circuitstructure formed therein.

In addition, the present invention may provide an electric vehicleincluding a pouch-shaped secondary battery having the short circuitstructure formed therein.

In addition, the present invention may provide a hybrid electric vehicleincluding a pouch-shaped secondary battery having the short circuitstructure formed therein.

In addition, the present invention may provide a power storage deviceincluding a pouch-shaped secondary battery having the short circuitstructure formed therein.

In addition, an increase in the volume (V_(short)) of the pouch-shapedbattery case for cutting the electrode tab and/or the electrode lead maysatisfy the condition of V_(short)>L on the assumption that the lengthof one side surface of the short circuit structure is L.

Here, V_(short) is defined as the state in which the length of one sidesurface of the short circuit structure is increased when the concaveunit and the convex unit of the short circuit structure are separatedfrom each other in the state in which the concave unit and the convexunit of the short circuit structure are normally coupled to each other.

Preferably, the condition of V_(short)>2L is satisfied.

In addition, an increase in the volume (V_(short)) of the pouch-shapedbattery case for cutting the electrode tab and/or the electrode lead maysatisfy the condition of Lc<0 on the assumption that the distancebetween a positive electrode cutting layer and a negative electrodecutting layer of the short circuit structure is Lc.

When the concave unit and the convex unit of the short circuit structureare separated from each other in the state in which the concave unit andthe convex unit of the short circuit structure are normally coupled toeach other, the cutting layers intersect each other. At this time, thecutting layers cut the electrode tab and/or the electrode lead insertedinto the hole. Consequently, Lc gradually decreases, and Lc has a valueof 0 when the cutting layers finally intersect each other. Afterwards,when the concave unit and the convex unit of the short circuit structurehave been completely separated from each other, Lc increases again. Aminus symbol is added to the length of Lc after the concave unit and theconvex unit of the short circuit structure are completely separated fromeach other.

The short circuit structure is formed in the sealed region of thepouch-shaped secondary battery. An adhesive layer formed at one surfaceof an upper pouch-shaped battery case is formed at at least one selectedfrom among the sealed region, the electrode tab, the electrode lead, andthe connection between the electrode tab and the electrode lead. Anadhesive layer formed at one surface of a lower pouch-shaped batterycase is formed at at least one selected from among the sealed region,the electrode tab, the electrode lead, and the connection between theelectrode tab and the electrode lead.

When the pressure in the secondary battery increases, force that deformsthe pouch-shaped sheathing member is applied to the upper surface andthe lower surface of the pouch-shaped sheathing member in oppositedirections. At this time, the two or more units of the short circuitstructure, which is formed in the sealed region of the pouch-shapedsecondary battery, are separated from each other, whereby at least oneselected from among the electrode tab, the electrode lead, and theconnection between the electrode tab and the electrode lead, which areinserted into the hole formed in the short circuit structure, may becut.

Although at least one selected from among the electrode tab, theelectrode lead, and the connection between the electrode tab and theelectrode is cut, only one of the electrode tab, the electrode lead, andthe connection between the electrode tab and the electrode lead may becut.

FIG. 8 is a view showing a positive electrode short circuit structureaccording to an embodiment of the present invention, wherein thepositive electrode short circuit structure includes three units.

The positive electrode short circuit structure includes a first shortcircuit structure unit, a second short circuit structure unit, and athird short circuit structure unit, which may be equally applied to anegative electrode. It is obvious that the electrode tab and/or theelectrode lead can be inserted into short circuit structure holes formedin the first short circuit structure unit, the second short circuitstructure unit, and the third short circuit structure unit. In addition,at least one side surface of each of the first short circuit structureunit and the third short circuit structure unit, in which the shortcircuit structure holes are not formed, may be disposed so as to be incontact with the pouch-shaped battery case.

At least one of the first short circuit structure unit, the second shortcircuit structure unit, and the third short circuit structure unit maybe provided at the at least one surface of the short circuit structurehole formed therein, which contacts the electrode tab and/or theelectrode lead inserted into the short circuit structure hole, with acutting layer for cutting the electrode tab and/or the electrode lead.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A pouch-shaped secondary battery configured to have a structure inwhich a unit cell, comprising a positive electrode plate, a separator, anegative electrode plate, an electrode tab, and an electrode lead, or acell assembly, constituted by two or more stacked unit cells, iscontained in a pouch-shaped battery case, wherein the pouch-shapedsecondary battery comprises a short circuit structure constituted by twoor more units, opposite ends of which are coupled to the electrode taband/or the electrode lead, for cutting the electrode tab and/or theelectrode lead when the pouch-shaped battery case is deformed due to anincrease in a volume of the pouch-shaped battery case.
 2. Thepouch-shaped secondary battery according to claim 1, wherein the shortcircuit structure is configured such that the two or more units of theshort circuit structure are separated from each other to cut theelectrode tab and/or the electrode lead when the pouch-shaped batterycase is deformed due to an increase in the volume of the pouch-shapedbattery case.
 3. The pouch-shaped secondary battery according to claim1, wherein the short circuit structure is provided at a predeterminedposition thereof with a hole, through which the electrode tab and/or theelectrode lead is inserted.
 4. The pouch-shaped secondary batteryaccording to claim 1, wherein the short circuit structure is formed atat least one selected from among the electrode tab, the electrode lead,and a connection between the electrode tab and the electrode lead. 5.The pouch-shaped secondary battery according to claim 1, wherein theelectrode tab is a positive electrode tab, a negative electrode tab, orboth the positive electrode tab and the negative electrode tab.
 6. Thepouch-shaped secondary battery according to claim 1, wherein theelectrode lead is a positive electrode lead, a negative electrode lead,or both the positive electrode lead and the negative electrode lead. 7.The pouch-shaped secondary battery according to claim 3, wherein theshort circuit structure comprises a concave unit and a convex unit, theconcave unit and the convex unit being coupled to each other.
 8. Thepouch-shaped secondary battery according to claim 3, wherein at leastone side surface of the short circuit structure, in which the hole isnot formed, is disposed so as to be in contact with the pouch-shapedbattery case.
 9. The pouch-shaped secondary battery according to claim7, wherein the short circuit structure is provided at at least onesurface of the hole formed therein, which contacts the electrode taband/or the electrode lead inserted into the hole, with a cutting layerfor cutting the electrode tab and/or the electrode lead.
 10. Thepouch-shaped secondary battery according to claim 9, wherein the cuttinglayer is made of at least one selected from among a metal material, aceramic material, and a polymer resin.
 11. The pouch-shaped secondarybattery according to claim 9, wherein the cutting layer, which contactsthe electrode tab and the electrode lead, is formed so as to have atleast one selected from among a quadrangular section, a circularsection, a semicircular section, a diamond-shaped section, an obliquesection, a wave section, a zigzag section, a sawtooth section, and anarbitrarily shaped section.
 12. A device comprising a pouch-shapedsecondary battery according to claim
 1. 13. The device according toclaim 12, wherein the device is selected from a group consisting of anelectronic device, an electric vehicle, a hybrid electric vehicle, and apower storage device.
 14. The pouch-shaped secondary battery accordingto claim 1, wherein an increase in the volume (V_(short)) of thepouch-shaped battery case for cutting the electrode tab and/or theelectrode lead satisfies a condition of (a) V_(short)>L (b) on anassumption that a length of one side surface of the short circuitstructure is L.
 15. The pouch-shaped secondary battery according toclaim 1, wherein an increase in the volume (V_(short)) of thepouch-shaped battery case for cutting the electrode tab and/or theelectrode lead satisfies a condition ofLc<0 on an assumption that a distance between a positive electrodecutting layer and a negative electrode cutting layer of the shortcircuit structure is Lc.